The present invention relates to espresso machines, and more particularly to improvements in espresso machines of the type capable of making cappuccino coffee.
It is well known to use an espresso machine for the making of cappuccino, i.e., a beverage containing coffee and frothed milk. A vessel, such as a cup, containing a plurality of milk is placed onto the base of an espresso machine at a level below the customary conduit which is provided with a steam discharging nozzle at its lower end. The nozzle is caused to dip into the body of milk and discharges steam. In order to promote the admission of air into the body of milk, the vessel is moved up and down relative to the nozzle so as to speed up the frothing process. Such procedure is time-consuming and requires a certain amount of expertise, namely proper positioning of the nozzle with reference to the vessel and a proper frequency and amplitude of up and down movements of the vessel. In addition, the just described mode of frothing milk in an espresso machine can cause injury or shock to the operator, for example, if the vessel contains a relatively small quantity of milk and the vessel is lowered to a level at which steam can escape above or close to the upper level of milk so that droplets of milk are sprayed all over and around the espresso machine including the garment of the operator.
It was further proposed to surround the nozzle of the steam supplying conduit with a cylindrical jacket through which air is drawn in response to opening of the valve which initiates the discharge of hot steam. The jacket has holes which are provided in its periphery and serve to admit air which is then sucked down the jacket and out at the lower end to penetrate into the body of milk. The jacket is further formed with at least one inlet for milk so that the lower part of the jacket contains a mixture of steam, air and milk. Such mixture leaves the conduit by way of the orifice in the nozzle and forms a froth. The just described machine exhibits the advantage that it is not necessary to move the vessel relative to the steam supplying conduit and that frothing of milk requires a minimum of expertise. On the other hand, the provision of a cylindrical jacket with openings for admission of air and milk contributes to the initial cost of the machine, especially if the jacket is to be removable so as to allow for convenient cleaning on a daily basis or at longer or shorter intervals.
The copending patent application Ser. No. 100,339 discloses an espresso machine with an attachment for the making of cappuccino wherein the attachment has a pipe with an open air admitting inlet at its upper end and an open air discharging outlet at its lower end. The steam conduit of this machine has an orifice for steam at its lower end, and the outlet of the pipe is positioned in such a way that steam issuing from the orifice draws air into the pipe by way of the inlet and out by way of the outlet to mix with steam and to frothe a quantity of milk when the resulting mixture is admitted into a body of milk in a cup or another vessel. The pipe can be a separately produced part which is separably and adjustably or integrally connected to the conduit. The copending application further discloses that the conduit can be provided with an integral portion which serves as an air supplying pipe and that it is possible to provide a coupling to separably connect the upper end of the conduit to the source of steam. An extension can be provided to allow mixing of air with steam before the resulting mixture is caused to enter into and to frothe a supply of milk. The extension can constitute an integral part of the conduit or a separately produced part which has a funnel-shaped portion surrounding a conical portion of the steam discharging nozzle of the conduit. The copending patent application further discloses that the inlet of the pipe can be provided with means for regulating the flow of air into the pipe by way of such inlet. The flow regulating means includes a valve, particularly a valve with a rotary valving element.
An advantage of the just described espresso machine is that suction in the relatively small funnelshaped portion of the extension suffices to draw air into the inlet of the pipe in a highly predictable manner. Moreover, the internal surfaces of the extension are not contacted by milk because the inflowing steam prevents milk from penetrating into the extension. This not only reduces the likelihood of contamination of the extension with milk but also prevents milk from clogging the relatively narrow passages for steam, air and mixture of air and steam. The purpose of the flow regulating means is to ensure that the user can conform the rate of admission of air to momentary requirements of the machine.